Belt shifter with curved fingers for multiple speed dryer

ABSTRACT

A belt shifter for shifting a drive belt on a drive pulley of a belt driving system for a clothes dryer in which the drive pulley has a tapered surface to provide a gradual increase in diameter which surface is provided with circular grooves which engage and receive circumferential grooves formed in a surface of the drive belt.

United States Patent H91 H11 3,707,882 Burkall 1 Jan. 2, 1973 [54] BELT SHIFTER WITH CURVED [56] References Cited FINGERS FOR MULTIPLE SPEED UNITED STATES PATENTS DRYER Inventor: Alvin E. Burkau st. p Mich. 1,136,116 4/1915 Furber ..74/242 [73] Assignee: Whirlpool Corporation, Benton Har- FOREIGN PATENTS OR APPLICATIONS I bor, Mich. 5,453 0/1910 Great Britain ..74/242.3 [22] Filed: June 1971 Primary Examiner-Leonard H. Gerin [21] App]. No.: 156,244 Atlorney-James S. Nettleton et a1.

7 [57] ABSTRACT [52] US. Cl. ..74/242.3, 68/140, 74/242.4

A belt shifter for shifting a drive belt on a drive pulley [51] r f 7/08 Do6fzl-loopq67f 23/700 of a belt driving system for a clothes dryer in which 1e 0 care s the drive p y has a tapered surface to provide a gradual increase in diameter which surface is provided with circular grooves which engage and receive circumferential grooves formed in a surface of the drive belt.

9 Claims, 7 Drawing Figures A ENT nJm sen 3. 707.882

sum 1 or 2 Q I INVENTOR.

BELT SHIFTER WITI-I CURVED FINGERS FOR MULTIPLE SPEED DRYER BACKGROUND OF THE INVENTION 1. Field of the Invention I The present invention is directed to a belt shifter particularly adapted for use in a belt drive system of a home appliance such as a clothes dryer.

2. Prior Art In home appliances such as clothes dryers, the rotation of the drying chamber or drum has been accomplished by using a belt driving system in which the belt is shifted axially on a drive pulley having surfaces of different diameters to enable changes in the speed of rotation of the dryer chamber or drum. An example of the structure using such a drive system is disclosed in the U.S. Pat. No. 3,365,810 which issued on Jan. 30, 1968, to T. S. Kotyuk et al.

In any belt drive system having variable speeds due to shifting of the belt on a pulley having drive surfaces of different diameters, problems will occur in attaining a smooth transition from one drive surface to another drive surface of the pulley without buckling or twisting the belt. Various structures for a belt shifting device have been proposed and the above-mentioned Kotyuk Patent, U.S. Pat. No. 750,576, issued on Jan. 26, 1904 to Pere and in U.S. Pat. No. 818,931, issued Apr. 24, 1906 to Bailey, are examples of structures used for belt shifting. In both the Pere and Bailey patents, the belt shifting means included surfaces that engaged the edge of the belt with one of the fingers pushing the belt towards the new position on the drive pulley and the opposite finger lifting the edge to facilitate movement between the two surfaces of pulleys. In each of these cases, the engagement of both edges of amoving belt during a shifting operation would create a large amount of friction on'the belt.

SUMMARY OF THE INVENTION drive surface of a drive pulley, the force applied thereto causes the belt to twist to raise the other edge away from the surface to facilitate a smooth transition between the drive portions of the drive pulley. The belt shifter finds particular utility in a belt drive having a drive pulley with a tapered drive surface provided with circular grooves which are engaged by circumferential grooves in the drive belt to cause the belt to twist during shifting to lift the grooves of the belt out of engagement with the grooves on the drive surface.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view, with portions broken away for purposes of illustration, of a laundry dryer utilizing a belt shifter and belt drive system of the present invention;

I drive system of the present invention;

FIG. 3 is an enlarged side elevation of the portion of the belt drive system illustrated in FIG. 2;

FIG. 4 is an enlarged fragmentary view of the belt shifter of the present invention;

FIG. 5 is a cross-section taken along line V--V of FIG. 4;

FIG. 6 is an enlarged fragmentary view similar to FIG. 4 during a shifting of the belt; and

FIG. 7 is an enlarged fragmentary view similar to FIG. 6 during a shifting of the belt in the direction opposite of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT The principles of the present invention are particularly adapted in a belt drive system generally indicated at 10 in FIG. 1. While the belt drive system 10 has utility in driving any object, it is particularly adapted for rotating a clothes dryer drum 1 l of a home dryer or appliance generally indicated at 12. The dryer 12 can be a conventional construction of a horizontal axis clothes dryer with the drum ll rotating on a horizontal axis. The drum 11 provides a chamber for receiving articles to be dried through an access door 13 in an outer casing 14 of the dryer 12 which has a control panel 15 having suitable controls such as push buttons 16 and rotary timing devices 17 for selecting a desired drying time, temperature or drying cycle. The dryer 12 has suitable means for heating the air and for circulating it through the drum 11 during the drying cycle. Located on the 26 which are attached to an internal frame portion 27 of the drying appliance 12. To transfer the rotary force of the drive pulley 22 to the drum 11, a belt 28 passes over the drive pulley 22 and around the outer surface of the drum 11. To maintain the belt 28 in tight engagement with the outer'surface of the drum 11, a belt tensioning means or slack takeup device 29 is provided and includes an idler pulley 30 rotatably mounted in a pulley hanger or bracket 31 which is pivotally mounted on a cylindrical bearing or pin 32 which projects from the bracket 25. To maintain the necessary tension on the belt 28, means such asa spring 33 biases the pulley hanger or bracket 31 in a counterclockwise direction as illustrated in FIG. 2 to take up any slack in the belt 28'.

As illustrated in FIG. 3, the drive pulley 22 has a tapering drive surface 35 which is provided with a plurality of axially spaced circular grooves 36 which have a V-shape to provide drive surface portions of different diameters or circumferences. The belt 28 is also provided with circumferentially extending V-shaped grooves 40 (FIG. 4) on the surface of the belt which engages the outer surface of the drum 11. Thus, during a driving action, the grooves 40 and the grooves 36 of the drive pulley 22 intermesh and coact to prevent or oppose axial displacement of the belt 28 on the grooved drive surface 35 of the drive pulley 22.

To shift the belt 28 axially on the drive pulley 22, the belt shifting device 21 has a finger unit 41 (FIG. 4). which includes a pair of finger members 42, a base member or connecting web 43, and a sleeve 44. Each of the finger units 42 has a finger portion 45 extending from a base portion 46, which finger portion has a convexed curved surface 47 extending in both longitudinal (along its length) and transverse directions (see FIG. 4 and 5). The pair of finger members 42 are arranged with the curved surfaces 47 facing each other by the connecting web 43 and the sleeve 44 which is received in flanged apertures 48 provided in each of the base portions 46.

To mount the finger unit 41 in the belt shifting device 21, the unit 41 is slidably mounted on the pin 32 betweenside flanges 50 (FIG. 3) of the pulley hanger 31 by having the sleeve 44 telescopically received on the pin. To prevent relative rotation of the unit 41 in at least one direction with respect to the pulley hanger 31,

means such asa lug 51 extending from the connecting web 43 and engaging an edge 52 of the hanger 31 is provided (FIG. 2). o

To shift the unit 41 axially on the pin 32, an inner cable or wire 54 of the control cable is attached to unit 41 to transfer any pivotal movement of the lever 19 to the finger unit. The outer sheath of the control cable 20 is illustrated as being connected to a pin 32 outside of the spaced side members 50 of the pulley hanger 31.

Preferably, the finger members 42 are formed of sheet metal by a stamping or embossing process which imparts the curvature to the finger portions 45 in'both directions and increases the rigidity of each finger portion in both the longitudinal and transverse direction. As illustrated, the pair of finger members 42, the web 43 and the stub 51 are formed as an integral unit. Also, the flanged apertures 48 can be formed during the stamping or embossing operation.

As best illustrated in FIG. 4, the pair of finger members 42 are spaced apart in the fingerunit 41 by the connecting web 43 and the sleeve 44 with the base portions 46 being substantially parallel. Thus, the curved surfaces 47 of the finger portion 45 extending above the sleeve 44 converge inwardly towards a narrow portion therebetween generally indicated at 60 and then diverge or flare outwardly. As best illustrated in FIGS. 2 and 4, the finger unit 41 is positioned with respect to the path of the belt 28 so that the belt passes between the pair of fingers 42 in a path between the narrow portion 60 and the ends of the fingers 42. Thus, the path'of the belt 28 is above the center of curvatures for the lon-.

gitudinal convex surface of the curved surface 47.

When the belt shifting device 21 is actuated by movement of the lever 19 of the speed control mechanism 18, the inner wire 54 of the control cable 20 applies a force to the finger unit 41 to urge the unit axially on the rod 32 in either direction depending on the direction of movement of the lever 19. If the unit 41 is moving in the direction indicated by the arrow 65 in FIG. 6, the curved surface 47 of the finger portion 45a engages an edge 28a of the belt 28 to apply a shifting force thereto. As the finger portion 45a applies a force to the edge 28a of the belt 28, the edge rides along the diverging curved surface 47 in a direction indicated by arrow 66 causing the other or leading edge 28b to tilt or twist in a downward direction. Thistwisting action which is caused by the force applied by the finger portion 45a, causes the leading edge 28b of the belt to be lifted from the surface of the drive pulley 22 and disengages the grooves 40 of the belt 28 from the circular grooves 36 to enable the shifting of the belt 28 axially on the pulley.

While it is contemplated that speed selection means or mechanism 18 will have three positions such as high, medium and low, the provision of a tapered drive surface 35 with circular grooves 36 enable smaller incremerits in the changeof the drive ratio between the pulley 22 and the belt 28. The smallest amount of change would be the axial movement of the belt 28 a distance equal to the width of one of the grooves 36 of the pulley 22.

Since the belt shifting device 21 applies through the. finger unit 41 a force to only one edge of the belt to cause the belt to twist and lift the other edge of the pulley surface, the amount of wear on the belt during a shifting operation is minimized and the shifterdoes not require a lifting of the belt by engaging both sides or edges of the belt during the shifting operation. The location of the finger unit 41 with respect to the belt, and the drive pulley 22. utilizes the twisting characteristic 'of the belt during a shifting to lift the grooves 40 of the belt 28 from the grooves 36 of the drive pulley.

During the shifting operation, any changes in v the length of the belt required for engaging the different diameter surfaces of the drive pulley 22 are compensated for by the tensioning device 29. As the belt shifts axially on the pulley 22, the belt 28 will also shift on the outer surface of the drum 11 a corresponding amount without applying any undesirable feedback which might tend to cause further shifting of the belt in either direction after the shifting device 2] has positioned the belt in the desired axial position on the variable diame ter pulley 22.

While pulley 22 has been described ashaving a tapered drive surface, it could belprovided with portions of the surface that have constant diametersthat are'interconnected by tapered portions. For example, the drive pulley could have a surface'portion of a constant diameter for high speed drive and a position of constant diameter for'low speed drive which portions are interconnected by a tapered'transitional or intermediate portion. Other configurations of the drive surface for a pulley such as 22 can be utilized with the belt shifting device 2I'of the present invention.

Although minor modifications'may be suggested those versed in theart, I wish to incorporate all-embodiments and modifications which come; within the scope of my contribution to the art.

I claim as my invention:

1. In a belt shifting device for moving a belt axially on a pulley between pulley surfaces of different diameters, said'shifting device having a pair of spaced apart fingers to provide a space for the belt to pass therebetween, said device including means to selectively move the device transversely to the belt path .to cause one of the fingers to apply a shifting force to the belt to axially move the belt on the pulley, the improvement comprising each of said pair of fingers having a convexed curved surface having a center of curvature with the fingers arranged with the convexsurfaces facing each other, and said device being positioned with respect to the path of the belt with said center of curvature of each of the fingers spaced below the belt so that when the belt is shifted one of the fingers engages said belt to apply a shifting force and causes twisting of the belt to lift the other edge from the surface of the pulley to facilitate axial movement therealong.

2. In a belt shifting device according to claim 1, wherein said convex curved surface extends along the length of the finger.

3. In a belt shifting device according to claim 1, wherein said convex surfaces of said fingers have a curvature extending in both a longitudinal and transverse direction for each finger,

4. In a belt shifting device according to claim 3, wherein the radius of curvature in each direction is different.

5. In a belt drive system for a dryer drum having a drive pulley with a surface of different diameters, a belt extending from the drive pulley and engaging the external surface of the dryer drum, means for tensioning' the belt and a belt shifter to move the belt axially on the pulley between said surfaces the improvement comprismg:

said belt having a surface having a plurality of circumferentially extending grooves;

said drive pulley having a drive surface with an axial taper, said tapered surface having a plurality of circular grooves provided thereon to coact with the one surface of the belt to oppose relative axial movement between the belt and the pulley surfaces, and

said belt shifter having a pair of fingers each of which have a longitudinally extending curved surface, said fingers being mounted on a base member with the curved surfaces in a facing relationship and the curved surfaces converging towards each other as the distance from the base member increases to a predetermined distance and then diverging from each other for the remaining distance from the base member, said base member being mounted with respect to the path of the belt with the belt passing between the fingers in the portion between the end of the fingers and the point of least distance therebetween so that as the belt shifter is actuated, one of the curved surfaces of the finger will engage the edge of the belt to apply a shifting force thereto to cause twisting of the belt to lift the grooves adjacent the other edge of the belt out of engagement with the grooves on the pulley surface to reduce the coaction therebetween which oppose the axial shiftirig of the belt.

6. In a belt drive system according to claim 5, wherein the actuating means for the shifter includes a flexible cable extending to a lever mounted on the dryer to enable an operator to shift the axial position of the belt on the pulley to vary the speed of rotation for the dryer drum.

7. In a belt drive system according to claim 5, wherein each of the fingers is a sheet metal member with the curved surface being a convex curved surface in both a longitudinal and transversed direction formed by embossing said sheet metal finger, said embossing increasing the stiffness of the finger to promote both transverse and longitudinal rigidity.

posite sides of the belt,

means for selectively moving said parts transversely of said belt and parallel to the axis of rotation of the drive pulley,

said parts comprising curved fingers engageable with said belt and operable to twist the belt thereby facilitating shifting of the belt.

9. A belt shifter as defined in claim 8 wherein said fingers are curved convexly and wherein the engagement of the belt is above the center of curvature of the parts. 

1. In a belt shifting device for moving a belt axially on a pulley between pulley surfaces of different diameters, said shifting device having a pair of spaced apart fingers to provide a space for the belt to pass therebetween, said device including means to selectively move the device transversely to the belt path to cause one of the fingers to apply a shifting force to the belt to axially move the belt on the pulley, the improvement comprising each of said pair of fingers having a convexed curved surface having a center of curvature with the fingers arranged with the convex surfaces facing each other, and said device being positioned with respect to the path of the belt with said center of curvature of each of the fingers spaced below the belt so that when the belt is shifted one of the fingers engages said belt to apply a shifting force and causes twisting of the belt to lift the other edge from the surface of the pulley to facilitate axial movement therealong.
 2. In a belt shifting device according to claim 1, wherein said convex curved surface extends along the length of the finger.
 3. In a belt shifting device according to claim 1, wherein said convex surfaces of said fingers have a curvature extending in both a longitudinal and transverse direction for each finger.
 4. In a belt shifting device according to claim 3, wherein the radius of curvature in each direction is different.
 5. In a belt drive system for a dryer drum having a drive pulley with a surface of different diameters, a belt extending from the drive pulley and engaging the external surface of the dryer drum, means for tensioning the belt and a belt shifter to move the belt axially on the pulley between said surfaces the improvement comprising: said belt having a surface having a plurality of circumferentially extending grooves; said drive pulley having a drive surface with an axial taper, said tapered surface having a plurality of circular grooves provided thereon to coact with the one surface of the belt to oppose relative axial movement between the belt and the pulley surfaces, and said belt shifter having a pair of fingers each of which have a longitudinally extending curved surface, said fingers being mounted on a base member with the curved surfaces in a facing relationship and the curved surfaces converging towards each other as the distance from the base member increases to a predetermined distance and then diverging from each other for the remainiNg distance from the base member, said base member being mounted with respect to the path of the belt with the belt passing between the fingers in the portion between the end of the fingers and the point of least distance therebetween so that as the belt shifter is actuated, one of the curved surfaces of the finger will engage the edge of the belt to apply a shifting force thereto to cause twisting of the belt to lift the grooves adjacent the other edge of the belt out of engagement with the grooves on the pulley surface to reduce the coaction therebetween which oppose the axial shifting of the belt.
 6. In a belt drive system according to claim 5, wherein the actuating means for the shifter includes a flexible cable extending to a lever mounted on the dryer to enable an operator to shift the axial position of the belt on the pulley to vary the speed of rotation for the dryer drum.
 7. In a belt drive system according to claim 5, wherein each of the fingers is a sheet metal member with the curved surface being a convex curved surface in both a longitudinal and transversed direction formed by embossing said sheet metal finger, said embossing increasing the stiffness of the finger to promote both transverse and longitudinal rigidity.
 8. A belt shifter for shifting a drive belt on a drive pulley of an appliance belt driving system comprising, first and second upstanding parts disposed on opposite sides of the belt, means for selectively moving said parts transversely of said belt and parallel to the axis of rotation of the drive pulley, said parts comprising curved fingers engageable with said belt and operable to twist the belt thereby facilitating shifting of the belt.
 9. A belt shifter as defined in claim 8 wherein said fingers are curved convexly and wherein the engagement of the belt is above the center of curvature of the parts. 